Tsarnaev, who is still hospitalized, reportedly told the U.S. Government that they had no help from international terrorist groups, with a source indicating that the Tsarnaev brothers fit the classification of self-radicalized jihadists.

Earlier Monday, Tsarnaev was formally charged with using a weapon of mass destruction at the Boston Marathon. The 19-year-old faces one count of using and conspiring to use an improvised explosive device resulting in death and one count of malicious destruction of property by means of an explosive device resulting in death. Tsarnaev could face the death penalty if convicted.

Tsarnaev and his older brother, who was killed after a shootout with police early Friday morning, are suspected of perpetrating the bombing at the Boston Marathon on April 15 that left three dead and over 200 people injured. Authorities also believe they intended to unleash more violence. The Boston Globereports police found a large quantity of IEDs, hand grenades, ammunition and other explosives.

Meanwhile, authorities reportedly want to speak with Tamerlan's wife, Katherine Russell, in hopes of gleaning any information she may have had about the attacks. "She knew nothing about it at any time," her attorney said in a statement.